This page will be ver y bor ing if your   br owser doesn't under stand Java. getDocumentBase() and getCodeBase()

Syntax : pu blic UR L getDocumentBase() Returns:

the UR L of the document that contains this a p plet. 

Gets the UR L of the document in which this a p plet is em bedded.

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For exam ple, su p pose an a p plet is contained within the document: htt p:// java.sun.com/ pr oducts/ jdk /1.2/index.html

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The document base is: htt p:// java.sun.com/ pr oducts/ jdk /1.2/index.html Syntax : pu blic UR L getCodeBase() Returns:

the base UR L of the dir ector y which contains this a p plet. 

Gets the base UR L. This is the UR L of the dir ector y which contains this a p plet.

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Exam ple segments:

UR L codeBase = getCodeBase(); Image myImage = getImage(codeBase, "images/myimage.gif "); Applet Context and showDocument() A p pletContext is an inter f ace that  pr ovides the means to contr ol the  br owser  envir onment in which the a p plet is r unning. The AudioClip Interf ace 

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The AudioC li p inter f ace is a sim ple a bstr action f or playing a sound cli p. Multi ple Audi oC li p items can  be  playing at the same time, and the r esulting sound is mixed together to pr oduce a com posite.

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Java and J2EE (06IS753) 

It has the f ollowing methods :

play

 pu blic a bstr act void play() • loop

Star ts playing this audio cli p. Each time this method is called, the cli p is r estar ted f r om the beginning.

• stop

 pu blic a bstr act void loo p()

 pu blic a bstr act void sto p() Sto ps playing this audio cli p. The AppletStub Interf ace

The A p pletStu b inter f ace  pr ovides a way to get inf or mation f r om the r un-time  br owser  envir onment. The A p plet class pr ovides methods with similar names that call these methods. Methods  publ ic ab st r act bool ean i s Act ive (   ) The isActive() method r etur ns the cur r ent state of the a p plet. While an a p plet is initializing, it is not active, and calls to isActive() r etur n f alse. The system mar k s the a p plet active  just  pr ior  to calling star t(); af ter this point, calls to isActive() r etur n tr ue. 

 publ ic ab st r act U   R L g et   Document   Ba se (   )

The getDocumentBase() method r etur ns the com plete UR L of  the HTML f ile that loaded the a p plet. This method can  be used with the getImage() or  getAudioCli p() methods to load an image or audio f ile r elative to the HTML f ile. 

 publ ic ab st r act U   R L g et C od e Ba se ( )

The getCodeBase() method r etur ns the com plete UR L of  the .cl a s s f ile that contains the a p plet. This method can  be used with the getImage() method or  the getAudioCli p() method to load an image or audio f ile r elative to the .cl a s s file. 

 publ ic ab st r act S t rin g  g et   P ar amet er ( S t r in g name)

The getPar ameter () method allows you to get  par ameter s f r om tags within the tag of the HTML f ile that loaded the a p plet. The name par ameter of getPar ameter () must match the name str ing of the tag; name is case insensitive. The r etur n value of  getPar ameter () is the value associated with name; it is always a Str ing r egar dless of  the ty pe of  data in the tag. If  name is not f ound within the tags of  the , getPar ameter () r etur ns null. 

 publ ic ab st r act  A p pl et C ont e xt  g et   A p pl et C ont e xt ( )

The getA p pletContext() method r etur ns the cur r ent A p pletContext of  the a p plet. This is  par t of  the stu b that is set by the system when setStu b() is called.

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Java and J2EE (06IS753) 

 publ ic ab st r act void a p pl et   Re si z e ( int wid t h , int hei g ht )

The a p pletR esize() method is called  by the r esize method of  the A p plet class. The method changes the size of  the a p plet s pace to width x height. The  br owser  must su p por t changing the a p plet s pace; if it doesn't, the size r emains unchanged Output To the Console

The dr awStr ing method can be used to out put str ings to the console. The position of the text can also be s pecif ied. The f ollowing pr og shows this conce pt:  pu blic class ConsolePr intA p plet1 extends java.a p plet.A p plet {  pu blic void init () { // Put code between this line dou ble x = 5.0; dou ble y = 3.0; System.out. pr intln( "x * y = "+ (x*y) ); System.out. pr intln( "x / y = "+ (x/y) ); // // and this line. } // Paint message in the a p plet window. Pu blic

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Java and J2EE (06IS753) UNIT-3 : MULTI THR EADED PR OGR AMMING, EVENT HANDLING Multi Threaded Programming:

What ar e thr eads? How to mak e the classes thr eada ble; Extending thr eads; Im plementing runna ble; Synchr onization; Changing state of  the thr ead; Bounded  buf f er  pr o blems, r ead-wr ite  pr o blem, pr oducer -consumer  pr oblems. Event Handling:

Two event handling mechanisms; The delegation event model; Event classes; Sour ces of  events; Event listener inter f aces; Using the delegation event model; Ada pter classes; Inner classes.

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Java and J2EE (06IS753) 3.1 What are Threads?

A thr ead is a single path of execution of code in a pr ogr am. 

A Multithr eaded pr ogr am contains two or mor e par ts that can r un concur r ently.

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Each par t of such a pr ogr am is called a Thr ead.

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Each thr ead def ines a se par ate path of execution. Multithr eading is a s pecialized f or m of Multitask ing.

3.1 How to mak e the classes threadable

A class can be made thr eada ble in one of the f ollowing ways (1) im plement the R unna ble Inter f ace and a p ply its r un() method. (2) extend the Thr ead class itself . 1. Im plementing R unna ble Inter f ace: The easiest way to cr eate a thr ead is to cr eate a class that im plements the R unna ble inter f ace. To im plement R unna ble, a class need only im plement a single method called r un(). The For mat of that f unction is pu blic void r un(). 2. Extending Thr ead: The second way to cr eate a thr ead is to cr eate a new class that extends the Thr ead class and then to cr eate an instance of  this class. This class must over r ide the run() method which is the entr y point f or the new thr ead. 1.2 Extending Threads

You can inher it the Thr ead class as another  way to cr eate a thr ead in your  pr ogr am. When you declar e an instance of  your  class, you’ll also have access to mem ber s of  the Thr ead class. Whenever  your  class inher its the Thr ead class, you must over r ide the r un() method, which is an entry into the new thr ead. The f ollowing exam ple shows how to inher it the Thr ead class and how to over r ide the r un() method. This exam ple def ines the MyThr ead class, which inher its the Thr ead class. The constr uctor  of  the MyThr ead class calls the constr uctor  of  the Thr ead class  by using the su per  k eywor d and  passes it the name of  the new thr ead, which is My thr ead. It then calls the star t() method to activate the new thr ead. The star t() method calls the r un() method of the MyThr ead class class MyThr ead extends Thr ead { MyThr ead() { su per ("My thr ead"); star t(); } SJBIT, Dept . of ISE

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Java and J2EE (06IS753)  pu blic void r un() { System.out. pr intln("Child thr ead star ted"); System.out. pr intln("Child thr ead ter minated"); }} class Demo {  pu blic static void main (Str ing ar gs[]){ new MyThr ead(); System.out p . r intln("Main thr ead star ted"); System.out. pr intln("Main thr ead ter minated"); }} 3.2 Implementing R unnable

The exam ple in the next segment demonstr ates the use of R unna ble and its im plementation. Synchronization

1. Two or mor e thr eads accessing the same data simultaneously may lead to loss of data integr ity. In or der to avoid this java uses the conce pt of monitor . A monitor is an o b ject used as a mutually exclusive lock . 2. At a time only one thr ead can access the Monitor . A second thr ead cannot enter the monitor  until the f ir st comes out. Till such time the other thr ead is said to be waiting. 3. The k eywor d Synchr onized is use in the code to ena ble synchr onization and it can be used along with a method. Changing the state of thread

Ther e might  be times when you need to tem por ar ily sto p a thr ead f r om  pr ocessing and then r esume  pr ocessing, such as when you want to let another  thr ead use the cur r ent r esour ce. You can achieve this o b jective by def ining your  own sus pend and r esume methods, as shown in the following exam ple. This exam ple def ines a MyThr ead class. The MyThr ead class def ines thr ee methods: the r un() method, the sus pendThr ead() method, and the r esumeThr ead() method. In addition, the MyThr ead class declar es the instance var ia ble sus pended, whose value is used to indicate whether or not the thr ead is sus pended. class MyThr ead im plements R unna ble { Str ing name; Thr ead t;

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Java and J2EE (06IS753)  boolean sus pended; MyThr ead() { t = new Thr ead(this, "Thr ead"); sus pended = f alse ; t.star t(); }  pu blic void r un() { tr y { for  (int i = 0; i < 10; i++) { System.out. pr intln("Thr ead: " + i ); Thr ead.slee p(200); synchr onized (this) { while (sus pended) { wait(); } } } } catch (Inter r u ptedExce ption e ) { System.out p . r intln("Thr ead: inter r u pted."); } System.out p . r intln("Thr ead exiting."); } void sus pendThr ead() { sus pended = tr ue; } synchr onized void r esumeThr ead() { sus pended = f alse; notif y(); } } class Demo {  pu blic static void main (Str ing ar gs [] ) { MyThr ead t1 = new MyThr ead(); tr y{ Thr ead.slee p(1000); Thr ead.slee p(1000);

SJBIT, Dept . of ISE

t1.sus pendThr ead();

System.out. pr intln("Thr ead:

Sus pended");

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Java and J2EE (06IS753) t1.r esumeThr ead(); System.out. pr intln("Thr ead: R esume"); } catch ( Inter r u ptedExce ption e) { } tr y { t1.t j . oin(); } catch ( Inter r u ptedExce ption e) { System.out. pr intln ( "Main Thr ead: inter r u pted"); } } } 3.3 Bounded Buf f er Problem Problem Description :

In com puter science the pr oducer -consumer  pr o blem (also k nown as the bounded-buf f er problem) is a classical exam ple of  a multi- pr ocess synchr onization  pr o blem. The  pr o blem descr i bes two pr ocesses, the pr oducer and the consumer , who shar e a

common, f ixed-size buf f er . The  pr oducer 's  jo b is to gener ate a  piece of  data,  put it into the  buf f er  and star t again. At the same time the consumer is consuming the data (i.e. r emoving it f r om the buf f er ) one piece at a time. The  pr o blem is to mak e sur e that the  pr oducer  won't tr y to add data into the  buf f er  if  it's full and that the consumer  won't tr y to r emove data f r om an em pty buf f er . This is the code f or  solving the a bove stated: class Buf f er Item {  pu blic volatile dou ble value = 0; // multi ple thr eads access  pu blic volatile  boolean occu pied = false; // so mak e these `volatile' } class BoundedBuf f er { // designed f or a single pr oducer thr ead and // a single consumer thr ead  pr ivate int numSlots = 0;  pr ivate Buf f er Item[] buf f er = null;  pr ivate int putIn = 0, tak eOut = 0; // pr ivate int count = 0;  pu blic BoundedBuf f er (int numSlots) {

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Java and J2EE (06IS753) if  (numSlots <= 0) thr ow new IllegalAr gumentExce ption("numSlots<=0"); this.numSlots = numSlots;  buf f er = new Buf f er Item[numSlots]; for (int i = 0; i < numSlots; i++) buf f er [i] = new Buf f er Item();  putIn = ( putIn + 1) % numSlots; // count++; // r ace condition!!! }  pu blic dou ble f etch() { dou ble value; while (! buf f er [tak eOut].occu pied) // busy wait Thr ead.cur r entThr ead().yield(); value = buf f er [tak eOut].value;

// C

 buf fer [tak eOut] .occu pied = f alse; //

// D tak eOut = (tak eOut + 1) % numSlots;

count--; // r ace condition!!! r etur n value;

} } Read-Write problem 

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R ead/Wr ite lock s pr ovides a synchr onization mechanism that allow thr eads in an a p plication to mor e accur ately r eflect the ty pe of access to a shar ed r esour ce that they r equir e. Many thr eads can acquir e the same r ead/wr ite lock  if  they acquir e a shar ed r ead lock  on the read/wr ite lock o b ject.

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Only one thr ead can acquir e an exclusive wr ite lock on a r ead/wr ite lock o b ject.

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When an exclusive wr ite lock is held, no other thr eads ar e allowed to hold any lock .  pu blic class R ead Wr iteLock {  pr ivate int r eader s = 0;  pr ivate int wr iter s = 0; pr ivate int wr iteR equests = 0;  pu blic synchr onized void lock R ead() thr ows Inter r u ptedExce ption{ while(wr iter s > 0 || wr iteR equests > 0){ wait(); } reader s++;

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Java and J2EE (06IS753) }  pu blic synchr onized void unlock R ead(){ r eader s--; notif yAll(); }  pu blic synchr onized void lock Wr ite() thr ows Inter r u ptedExce ption{ wr iteR equests++; while(r eader s > 0 || wr iter s > 0){ wait(); } wr iteR equests--; wr iter s++; }  pu blic synchr onized void unlock Wr ite() thr ows Inter r u ptedExce ption{ wr iter s--; notif yAll(); } } Producer-Consumer problems 

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In  pr oducer /consumer  synchr onizations,  pr oducer   pr ocesses mak e items availa ble to consumer  processes. Exam ples ar e a message sender and a message r eceiver , or two machines wor k ing on items in sequence. The synchr onization her e must ensur e that the consumer  pr ocess does not consume mor e items than have  been  pr oduced. If  necessar y, the consumer  pr ocess is  block ed (must wait) if no item is availa ble to be consumed. Pr oducer  and consumer   pr ocesses ar e cou pled  by a  buf f er  to allow asynchr onous  pr oduction and consum ption. The  buf f er  can  be  bounded (have a ca pacity limit) or  un bounded ( be a ble to stor e an unlimited num ber of items).

3.4 Event Handling

In Java, events r e pr esent all activity that goes on between the user and the a p plication.

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Java and J2EE (06IS753) Two event handling mechanisms :

Delegation event model : It def ines standar d and consistent mechanisms to gener ate and  pr ocess events. Her e the sour ce gener ates an event and sends it to on or  mor e listener s. The listener  sim ply waits until it r eceives an event. Once it is o btained, It  pr ocesses this event and retur ns. Listener s should r egister  themselves with a sour ce in or der  to r eceive an even notif ication. Notif ications ar e sent only to listener s that want to r eceive them. Events

In the delegation model, an event is an o b ject that descr i bes a state change in a sour ce. It can be gener ated as a consequence of  a  per son inter acting with the elements in a gr a phical user  inter f ace. Some of  the activities that cause events to  be gener ated ar e :  pr essing a  button, enter ing a char acter  via the k ey boar d, selecting an item in a list, and click ing the mouse. Events may also occur  that ar e not dir ectly caused  by inter actions with a user  inter f ace. For  exam ple, an event may  be gener ated when a timer  ex pir es, a counter  exceeds a value, a sof twar e or har dwar e f ailur e occur s, or an o per ation is com pleted. Event Classes

The classes that r e pr esent events ar e at the cor e of  Java’s event handling mechanism. EventOb ject : It is at the r oot of the Java event class hier ar chy in java.util. It is the su per class f or  all events. Its one constr uctor  is shown her e: EventO b ject(O b ject  sr c ) Her e,  sr c is the o b ject that gener ates this event. EventO b ject contains two methods: getSour ce( ) and toStr ing( ). The getSour ce( ) method r etur ns the sour ce of the event. EventOb ject is a su per class of all events. The ActionEvent Class :

An ActionEvent is gener ated when a button is pr essed, a list item is dou ble-click ed, or a menu item is selected. The ActionEvent class def ines f our  integer  constants that can  be used to identif y any modif ier s associated with an action event: ALT _ MASK , CTR L _ MASK , META _ MASK , and SHIFT _ MASK . ActionEvent has these thr ee constr uctor s: ActionEvent(O b ject sr c ,

int t   y pe , Str ing cmd   ) ActionEvent(O b ject sr c , int t y pe , Str ing cmd   , int mod i f ier   s ) ActionEvent(O b ject sr c , int t   y pe , Str ing cmd   , long when , int mod i f ier   s ) Her e, sr c is a r ef er ence to the o b ject that gener ated this event. The ty pe of  the event is s pecif ied  by t   y pe , and its command str ing is cmd . The ar gument mod i f ier   s indicates which modif ier  k eys (ALT, CTR L, META, and/or  SHIFT) wer e  pr essed when the event was gener ated. The when  par ameter  s pecif ies when the event occur r ed 

The Ad justmentEvent Class An Ad justmentEvent is gener ated by a scr oll bar 

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Java and J2EE (06IS753) The ComponentEvent Class A ComponentEvent is gener ated when the size,  position, or  visi bility of  a com ponent is changed. Ther e ar e f our  ty pes of  com ponent events 

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The ContainerEvent Class A ContainerEvent is gener ated when a com ponent is added to or r emoved f r om a container  The FocusEvent Class : A FocusEvent is gener ated when a com ponent gains or  loses in put f ocus The InputEvent Class : The a bstr act class InputEvent is a su bclass of  ComponentEvent and is the su per class f or  com ponent in put events. Its su bclasses ar e K eyEvent and MouseEvent. The ItemEvent Class : An ItemEvent is gener ated when a check  box or  a list item is click ed or when a check a ble menu item is selected or deselected

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The K eyEvent Class A K eyEvent is gener ated when k ey boar d in put occur s.

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The MouseEvent Class Ther e ar e eight ty pes of mouse events

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The MouseWheelEvent Class The MouseWheelEvent class enca psulates a mouse wheel event. The TextEvent Class Instances of  this class descr i be text events. These ar e gener ated

 by text f ields and text ar eas when char acter s ar e enter ed by a user or  pr ogr am. 

The WindowEvent Class Ther e ar e ten ty pes of window events. The WindowEvent

class def ines integer constants that can be used to identif y them. Sources of Events

Event Sour ce Descr i ption : 

Button - Gener ates action events when the button is pr essed.

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Check box - Gener ates item events when the check  box is selected or deselected.

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Choice - Gener ates item events when the choice is changed.

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List - Gener ates action events when an item is dou ble-click ed; gener ates item events

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when an item is selected or deselected.

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Menu Item - Gener ates action events when a menu item is selected; gener ates item

events when a check a ble menu item is selected or deselected. SJBIT, Dept . of ISE

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Java and J2EE (06IS753) 

Scrollbar - Gener ates ad justment events when the scr oll bar is mani pulated.

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Text components - Gener ates text events when the user enter s a char acter .

Window - Gener ates window events when a window is activated, closed, deactivated, 

deiconif ied, iconif ied, o pened, or quit. Event Listener Interf aces

Listener s ar e cr eated  by im plementing one or  mor e of  the inter f aces def ined  by the  java.awt.event pack age. When an event occur s, the event sour ce invok es the a p pr o pr iate method def ined by the listener  and pr ovides an event o b ject as its ar gument. Interf ace Description ActionListener - Def ines one method to r eceive action events. Ad justmentListener - Def ines one method to r eceive ad justment events. ComponentListener - Def ines f our methods to r ecognize when a com ponent is hidden, moved, r esized, or shown. ContainerListener - Def ines two methods to r ecognize when a com ponent is added to or  removed f r om a container . FocusListener - Def ines two methods to r ecognize when a com ponent gains or loses k ey boar d focus. ItemListener - Def ines one method to r ecognize when the state of an item changes. KeyListener - Def ines thr ee methods to r ecognize when a k ey is pr essed, r eleased, or ty ped. MouseListener - Def ines f ive methods to r ecognize when the mouse is click ed, enter s a com ponent, exits a com ponent, is pr essed, or is r eleased. MouseMotionListener - Def ines two methods to r ecognize when the mouse is dr agged or  moved. MouseWheelListener - Def ines one method to r ecognize when the mouse wheel is moved. TextListener - Def ines one method to r ecognize when a text value changes. WindowFocusListener - Def ines two methods to r ecognize when a window gains or  loses in put f ocus. WindowListener Def ines seven methods to r ecognize when a window is activated, closed, deactivated, deiconif ied, iconif ied, o pened, or quit. Using the Delegation Event Model

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Java and J2EE (06IS753) A p plet pr ogr amming using the delegation event model is done f ollowing these two ste ps: 1. Im plement the a p pr o pr iate inter f ace in the listener  so that it will r eceive the ty pe of  event desir ed. 2. Im plement code to r egister  and unr egister  (if  necessar y) the listener  as a r eci pient f or  the event notif ications. Adapter Classes

Def inition : An ada pter  class  pr ovides an em pty im plementation of  all methods in an event listener inter f ace. 





Ada pter  classes ar e usef ul when you want to r eceive and  pr ocess only some of  the events that ar e handled by a par ticular event listener inter f ace.  New class to act as an event listener   by extending one of  the ada pter  classes and im plementing only those events in which you ar e inter ested. For  exam ple, the MouseMotionAdapter class has two methods, mouseDragged( ) and mouseMoved( ). The signatur es of  these em pty methods ar e exactly as def ined in the MouseMotionListener inter f ace. If  you wer e inter ested in only mouse dr ag events, then you could sim ply extend MouseMotionAdapter and im plement mouseDragged( ). The em pty im plementation of mouseMoved( ) would handle the mouse motion events f or you.

The f ollowing exam ple demonstr ates an ada pter . // Demonstr ate an ada pter . im por t java.awt.*; im por t java.awt.event.*; im por t java.a p plet. *; /* */  pu blic class Ada pter Demo extends A p plet {  pu blic void init() { addMouseListener (new MyMouseAda pter (this)); addMouseMotionListener (new MyMouseMotionAda pter (this)); }} class MyMouseAda pter extends MouseAda pter { Ada pter Demo ada pter Demo; SJBIT, Dept . of ISE

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Java and J2EE (06IS753)  pu blic MyMouseAda pter (Ada pter Demo ada pter Demo) { this.ada pter Demo = ada pter Demo; } // Handle mouse click ed.  pu blic void mouseClick ed(MouseEvent me) { ada pter Demo.showStatus("Mouse click ed"); }} class MyMouseMotionAda pter extends MouseMotionAda pter { Ada pter Demo ada pter Demo;  pu blic MyMouseMotionAda pter (Ada pter Demo ada pter Demo) { this.ada pter Demo = ada pter Demo; } // Handle mouse dr agged.  pu blic void mouseDr agged(MouseEvent me) { ada pter Demo.showStatus("Mouse dr agged"); }} Inner Classes

Consider  the a p plet shown in the f ollowing listing. It dis play the str ing

d oe s not  use

an inner  class. Its goal is to

“Mouse Pr essed” in the status  bar  of  the a p plet viewer  or  br owser  when the mouse is  pr essed. Ther e ar e two to p-level classes in this  pr ogr am. MousePressedDemo extends Applet, and MyMouseAdapter extends MouseAdapter. The init( ) method of  MousePressedDemo instantiates MyMouseAdapter and  pr ovides this o b ject as an ar gument to the addMouseListener( ) method.  Notice that a r ef er ence to the a p plet is su p plied as an ar gument to the MyMouseAdapter constr uctor . This r ef er ence is stor ed in an instance var ia ble f or later use by the mousePressed( ) method. // This a p plet does NOT use an inner class. im por t java.a p plet. *; SJBIT, Dept . of ISE

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Java and J2EE (06IS753) im por t java.awt.event.*; /* */  pu blic class MousePr essedDemo extends A p plet {  pu blic void init() { addMouseListener (new MyMouseAda pter (this)); }} class MyMouseAda pter extends MouseAda pter { MousePr essedDemo mousePr essedDemo;  pu blic MyMouseAda pter (MousePr essedDemo mousePr essedDemo) { this.mousePr essedDemo = mousePr essedDemo; }  pu blic void mousePr essed(MouseEvent me) { mousePr essedDemo.showStatus("Mouse Pr essed.");

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) UNIT-4: SWINGS SWINGS:

The or igins of Swing; Two k ey Swing f eatur es; Com ponents and Container s; The Swing Pack ages; A sim ple Swing A p plication; Cr eate a Swing A p plet; Jla bel and ImageIcon; JTextField; The Swing Buttons; JTa b bed pane; JScr ollPane; JList; JCom boBox; JTa ble.

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) Swing is  built on to p of  AWT and is entir ely wr itten in Java, using AWT’s lightweight com ponent su p por t. In  par ticular , unlik e AWT, t he ar chitectur e of  Swing com ponents mak es it easy to customize  both their  a p pear ance and  behavior . Com ponents f r om AWT and Swing can  be mixed, allowing you to add Swing su p por t to existing AWT- based  pr ogr ams. For  exam ple, swing com ponents such as JSlider , JButton and JCheck   box could  be used in the same  pr ogr am with standar d AWT la bels, textf ields and scr oll bar s. 4.1 Three parts

Com ponent set (su bclasses of JCom ponent) Su p por t classes, Inter f aces Swing Components and Containers

Swing com ponents ar e basic building block s of an a p plication. Swing toolk it has a wide r ange of var ious widgets. Buttons, check  boxes,slider s, list boxes etc. Ever ything a pr ogr ammer  needs f or his jo b. In this section of the tutor ial, we will descr i be sever al usef ul com ponents. JLa bel Com ponent JLabel is a sim ple com ponent f or dis playing text, images or  both. It does not r eact to in put events.

JCheck Box JCheck Box is a widget that has two states. On and Of f . It is a box with a la bel JSlider  JSlider is a com ponent that lets the user gr a phically select a value by sliding a k no b within a  bounded inter val JCom boBox Com bo box is a com ponent that com bines a button or edita ble f ield and a dr o p-down list. The user can select a value f r om the dr o p-down list, which a p pear s at the user 's r equest. JPr ogr essBar  A pr ogr ess bar is a widget that is used, when we pr ocess lengthy task s. It is animated so that the user k nows, that our task is pr ogr essing JToggleButton

JToggleButton is a button that has two states. Pr essed and not pr essed. You toggle between these two states by click ing on it Containers

Swing contains a num ber of com ponents that pr ovides f or gr ou ping other com ponents together .

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) In AWT, such com ponents extended java.awt.Container and included Panel, Window, Fr ame, and Dialog. 1.1 A Simple Container JPanel is Swing’s ver sion of the AWT class Panel and uses the same def ault layout, FlowLayout. JPanel is descended dir ectly f r om JCom ponent. JFrame is Swing’s ver sion of Fr ame and is descended dir ectly f r om that class. The com ponents added to the f r ame ar e r ef er r ed to as its contents; these ar e managed by the contentPane. To add a com ponent to a JFr ame, we must use its contentPane instead. JInternalFrame is conf ined to a visi ble ar ea of a container it is placed in. It can be iconif ied , maximized and layer ed. JWindow is Swing’s ver sion of Window and is descended dir ectly f r om that class. Lik e Window, it uses Bor der Layout by def ault. JDialog is Swing’s ver sion of Dialog and is descended dir ectly f r om that class. Lik e Dialog, it uses Bor der Layout by def ault. Lik e JFr ame and JWindow,

JDialog contains a r ootPane hier ar chy including a contentPane, and it allows layer ed and glass  panes. All dialogs ar e modal, which means the cur r ent thr ead is block ed until user inter action with it has been com pleted. JDialog class is intended as the basis f or cr eating custom dialogs; however , some of the most common dialogs ar e pr ovided thr ough static methods in the class JO ptionPane. Jlabel and ImageIcon

Syntax :

 pu blic class JLabel

extends JCom ponent im plements SwingConstants, Accessi ble 

It is a dis play ar ea f or a shor t text str ing or an image, or  both.



A la bel does not r eact to in put events. As a r esult, it cannot get the k ey boar d f ocus.



A la bel can dis play a k ey boar d alter native as a convenience f or a near   by com ponent that has a k ey boar d alter native but can't dis play it.



A JLa bel o b ject can dis play either text, an image, or  both.



By def ault, la bels ar e ver tically center ed in their dis play ar ea.



Text-only la bels ar e leading edge aligned, by def ault; image-only la bels ar e hor izontally center ed, by default.

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) • Can use the setIconTextGa p method to s pecif y how many pixels should a p pear  between the text and the image. The def ault is 4 pixels. ImageIcon

Syntax :  pu blic ImageIcon(Str ing filename) { this(f ilename, f ilename); } Cr eates an ImageIcon f r om the s pecif ied f ile. The image will be pr eloaded by using MediaTr ack er to monitor the loading state of the image. The s pecif ied Str ing can be a f ile name or a f ile path. When s pecif ying a path, use the Inter netstandar d f or war d-slash ("/") as a se par ator . (The string is conver ted to an UR L, so the f or war dslash wor k s on all systems.) For exam ple, s pecif y: new ImageIcon("images/myImage.gif ") The descr i ption is initialized to the f ilename str ing. Exam ple of JLa bel with ImageIcon : import java.awt.FlowLayout; import java.awt.HeadlessExce ption; import javax.swing.Icon; import javax.swing.ImageIcon; import javax.swing.JFr ame; import javax.swing.JLa bel; public class Main extends JFr ame { public Main() throws HeadlessExce ption { setSize(300, 300);

setDef aultCloseO per ation(JFr ame.EXIT _ O N _ CLOSE); setLayout(new FlowLayout(FlowLayout.LEFT)); Icon icon = new ImageIcon("a p . ng"); JLa bel la bel1 = new JLa bel("Full Name :", icon, JLa bel.LEFT); JLa bel la bel2 = new JLa bel("Addr ess :", JLa bel.LEFT); la bel2.setIcon(new ImageIcon(" b p . ng")); getContentPane().add(la bel1); getContentPane().add(la bel2); } SJBIT, Dept . of ISE

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Java and J2EE (06IS753) public static void main(Str ing[] ar gs) { new Main().setVisi ble(true);

} } JTextField 

JTextField is a lightweight com ponent that allows the editing of a single line of text.



JTextField is intended to be sour ce-com pati ble with java.awt.TextField wher e it is reasona ble to do so. This com ponent has ca pa bilities not f ound in the  java.awt.TextField class.





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JTextField has a method to esta blish the str ing used as the command str ing f or the action event that gets f ir ed. The java.awt.TextField used the text of the f ield as the command str ing f or the ActionEvent. JTextField will use the command str ing set with the setActionCommand method if not null, other wise it will use the text of the f ield as a com pati bility with java.awt.TextField.

1. Swing Pack age

Syntax :  pu blic class JButton extends A bstr actButton im plements Accessi ble An im plementation of a " push" button. Buttons can be conf igur ed, and to some degr ee contr olled, by Actions. Using an Action with a button has many benef its beyond dir ectly conf igur ing a button.  pack age com.ack .gui.swing.sim ple; im por t java.awt.*; im por t java.awt.event.WindowAda pter ; im por t java.awt.event.WindowEvent; im por t  javax.swing.*;  pu blic class Sim pleSwingButtons extends JFr ame {  pu blic static void main( Str ing[] ar gv ) { Sim pleSwingButtons myExam ple = new Sim pleSwingButtons( "Sim ple Swing Buttons" ); }

SJBIT, Dept . of ISE

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Java and J2EE (06IS753)  pu blic Sim pleSwingButtons( Str ing title ) { su per ( title ); setSize( 150, 150 ); add WindowListener ( new WindowAda pter () { pu blic void windowClosing( WindowEvent we ) { dis pose(); System.exit( 0 ); } } ); init(); setVisi ble( tr ue ); }  pr ivate void init() { JPanel my _   panel = new JPanel(); my _   panel.setLayout( new Gr idLayout( 3, 3 ) ); f or ( int i = 1; i < 10; i++ ) { ImageIcon icon = new ImageIcon( i + ".gif " ); JButton j b = new JButton( icon );  j b.setToolTi pText( i + ".gif " ); my _   panel.add( j b ); } getContentPane().add( my _   panel ); my _   panel.setBor der ( Bor der Factor y.cr eateEtchedBor der () ); } } JTabbedpane

Syntax : pu blic class JTa b bedPane extends JCom ponent im plements Ser ializa ble, Accessi ble, SwingConstants 

A com ponent that lets the user switch between a gr ou p of com ponents by click ing on a ta b with a given title and/or icon.

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) 





Ta bs/com ponents ar e added to a Ta b bedPane o b ject by using the addTa b and inser tTab methods. A ta b is r e pr esented by an index cor r es ponding to the position it was added in, wher e the fir st ta b has an index equal to 0 and the last ta b has an index equal to the ta b count minus The Ta b bedPane uses a Single SelectionModel to r e pr esent the set of ta b indices and the cur r ently selected index. If the ta b count is gr eater than 0, then ther e will always be a selected index, which by def ault will be initialized to the f ir st ta b. If the ta b count is 0, then the selected index will be -1.

JScrollPane

Syntax : pu blic class JScr ollPane extends JCom ponent im plements Scr ollPaneConstants, Accessi ble 







Pr ovides a scr olla ble view of a lightweight com ponent. A JScr ollPane manages a view por t, o ptional ver tical and hor izontal scr oll bar s, and o ptional r ow and column heading view por ts. The JView por t pr ovides a window, or "view por t" onto a data sour ce -- f or exam ple, a text f ile. That data sour ce is the "scr olla ble client" (ak a data model) dis played by the JView por t view. A JScr ollPane basically consists of JScr ollBar s, a JView por t, and the wir ing between them, as shown in the diagr am at r ight.

JList

Syntax : pu blic class JList extends JCom ponent im plements Scr olla ble, Accessi ble A com ponent that allows the user to select one or mor e o b jects f r om a list. A se par ate model, ListModel, r e pr esents the contents of the list. // Cr eate a JList that dis plays the str ings in data[] Str ing[] data = {"one", "two", "thr ee", "f our "}; JList dataList = new JList(data); JComboBox

Syntax : pu blic class JCom boBox extends JCom ponent SJBIT, Dept . of ISE

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Java and J2EE (06IS753) im plements ItemSelecta ble, ListDataListener , ActionListener , Accessi ble 

A com ponent that com bines a button or edita ble f ield and a dr o p-down list.



The user can select a value f r om the dr o p-down list, which a p pear s at the user 's r equest.



If you mak e the com bo box edita ble, then the com bo box includes an edita ble f ield into which the user can ty pe a value.

JTable

Syntax : pu blic class JTa ble extends JCom ponent im plements Ta bleModelListener , Scr olla ble, Ta bleColumnModelListener , ListSelectionListener , CellEditor Listener , Accessi ble

•

The JTa ble is used to dis play and edit r egular two-dimensional ta bles of cells.

•

The JTa ble has many f acilities that mak e it possi ble to customize its r ender ing and

editing but pr ovides def aults f or these f eatur es so that sim ple ta bles can be set up easily. •

For exam ple, to set u p a ta ble with 10 r ows and 10 columns of num ber s:

Ta bleModel dataModel = new A bstr actTa bleModel() {  pu blic int getColumnCount() { r etur n 10; }  pu blic int getR owCount() { r etur n 10;}  pu blic O b ject getValueAt(int r ow, int col) { r etur n new Integer (r ow*col); } } JTa ble ta ble = new JTa ble(dataModel); JScr ollPane scr oll pane = new JScr ollPane(ta ble);

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) UNIT-5: JAVA 2 ENTER PR ISE EDITION OVER VIEW, DATABASE ACCESS:

Over view of J2EE and J2SE. The Conce pt of JDBC JDBC Dr iver Ty pes; JDBC Pack ages; A Br ief  Over view of  the JDBC  pr ocess; Data base Connection; Associating the JDBC/ODBC Br idge with the Data base; Statement O b jects; R esultSet; Tr ansaction Pr ocessing; Metadata, Data ty pes; Exce ptions.

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) Overview of J2EE and J2SE 





™

™

Java 2 Platf or m, Enter   pr ise Edition (J2EE ) technology pr ovides a com ponent based a p pr oach to the design, develo pment, assem bly, and de ployment of  enter   pr ise a p plications. The J2EE platf or m gives you a multitier ed distr i buted a p plication model, the a bility to r euse com ponents, integr ated XML- based data inter change, a unif ied secur ity model, and f lexi ble tr ansaction contr ol. Vendor s and customer s en joy the f r eedom to choose the pr oducts and com ponents that best meet their  business and technological r equir ements.

5. 1 The Concept of JDBC 

The JDBC ( Java Data base Connectivity) API def ines inter f aces and classes f or  wr iting data base a p plications in Java by mak ing data base connections.



Using JDBC you can send SQL, PL/SQL statements to almost any r elational data base. JDBC is a Java API f or executing SQL statements and su p por ts basic SQL functionality.



It pr ovides R DBMS access by allowing you to em bed SQL inside Java code.

Overview of JDBC Process

Bef or e you can cr eate a java jd bc connection to the data base, you must f ir st im por t the java.sql  pack age. im por t java.sql.*; The star ( * ) indicates that all of the classes in the pack age java.sql ar e to be im por ted. Java a p plication calls the JDBC li br ar y. JDBC loads a dr iver which talk s to the data base. We can change data base engines without changing data base code. Esta blishing Data base Connection and Associating JDBC/ODBC br idge 1. Loading a database driver, In this ste p of the jd bc connection pr ocess, we load the dr iver class by calling Class.f or   Name() with the Dr iver class name as an ar gument. Once loaded, the Dr iver class cr eates an instance of  itself .



A client can connect to Data base Ser ver thr ough JDBC Dr iver . Since most of the Data base ser ver s su p por t ODBC dr iver ther ef or e JDBC-ODBC Br idge dr iver is commonly used.

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The r etur n ty pe of the Class.f or   Name (Str ing Class Name) method is “Class”. Class is a class in  java.lang pack age.

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SJBIT, Dept . of ISE

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Java and J2EE (06IS753) Class.f or   Name(”sun j . d bc.od bc.Jd bcOd bcDr iver ”); //Or any other dr iver  } catch(Exce ption x) { System.out. pr intln( “Una ble to load the dr iver class!” ); } 5.2 Creating a oracle jdbc Connection

The JDBC Dr iver Manager class def ines o b jects which can connect Java a p plications to a JDBC dr iver . Dr iver Manager is consider ed the back   bone of JDBC ar chitectur e. Dr iver Manager class manages the JDBC dr iver s that ar e installed on the system. 

Its getConnection() method is used to esta blish a connection to a data base. It uses

a user name, passwor d, and a jd bc ur l to esta blish a connection to the data base and retur ns a connection o b ject. 



A jd bc Connection r e pr esents a session/connection with a s pecif ic data base. Within the context of a Connection, SQL, PL/SQL statements ar e executed and r esults ar e r etur ned. An a p plication can have one or mor e connections with a single data base, or it can have many connections with dif f er ent data bases. A Connection o b ject pr ovides metadata i.e. inf or mation a bout the data base, ta bles, and fields. It also contains methods to deal with tr ansactions.

•Each su b pr otocol has its own syntax f or the sour ce. We’r e using the jd bc od bc su b pr otocol, so the Dr iver Manager k nows to use the sun j . d bc.od bc.Jd bcOd bcDr iver . tr y{ Connection d bConnection=Dr iver Manager .getConnection(ur l,”login Name”,”Pas swor d”) } catch( SQLExce ption x ){ System.out. pr intln( “Couldn’t get connection!” ); } 5.3. Creating a JDBC Statement ob ject 

Once a connection is o btained we can inter act with the data base.

Connection inter f ace def ines methods f or inter acting with the data base via the esta blished connection. SJBIT, Dept . of ISE

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Java and J2EE (06IS753) 

To execute SQL statements, you need to instantiate a Statement o b ject f r om your connection o b ject by using the cr eateStatement() method.

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Statement statement = d bConnection.cr eateStatement();

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A statement o b ject is used to send and execute SQL statements to a data base.

Thr ee kinds of Statements 

Statement: Execute sim ple sql quer ies without par ameter s.

Statement cr eateStatement() Cr eates an SQL Statement o b ject. 

Prepared Statement: Execute pr ecom piled sql quer ies with or without par ameter s. Pr e p ar edS tatement pr e par e Statement(Str ing sql)

r etur ns a new Pr e par edStatement o b ject. Pr e p ar edStatement o b jects ar e pr ecom piled SQL statements. 

Callable Statement: Execute a call to a data base stor ed pr ocedur e. Calla bleStatement  pr e par eCall(Str ing sql)

retur ns a new Calla bleStatement o b ject. Calla bleStatement o b jects ar e SQL stor ed pr ocedur e call statements. 5.4. Executing a SQL statement with the Statement ob ject, and returning a jdbc resultSet. 



Statement inter f ace def ines methods that ar e used to inter act with data base via the execution of SQL statements. The Statement class has thr ee methods f or executing statements: executeQuer y(), executeU pdate(), and execute(). For a SELECT statement, the method to use is executeQuer y .

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

For  statements that cr eate or  modif y ta bles, the method to use is executeU pdate.  Note: Statements that cr eate a ta ble, alter  a ta ble, or  dr o p a ta ble ar e all exam ples of  DDL statements and ar e executed with the method executeU pdate. execute() executes an SQL statement that is wr itten as Str ing o b ject.

R esultSet pr ovides access to a ta ble of data gener ated by executing a Statement. The ta ble r ows ar e r etr ieved in sequence. A R esultSet maintains a cur sor  pointing to its cur r ent r ow of data. The next() method is used to successively ste p thr ough the r ows of the ta bular r esults. R esultSetMetaData Inter f ace holds inf or mation on the ty pes and pr o per ties of the columns in a ResultSet. It is constr ucted f r om the Connection o b ject.

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) UNIT -6: SER VLETS

Back gr ound; The Lif e Cycle of a Ser vlet; Using Tomcat f or  Ser vlet Develo pment; A sim ple Ser vlet; The Ser vlet API; The Javax.ser vlet Pack age; R eading Ser vlet Par ameter ; The Javax.ser vlet.htt p pack age; Handling HTTP R equests and R es ponses; Using Cook ies; Session Tr ack ing

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) Back ground

Def inition : Ser vlets ar e modules of Java code that r un in a ser ver a p plication (hence the name "Ser vlets", similar to "A p plets" on the client side) to answer client r equests. 



Ser vlets ar e not tied to a s pecif ic client-ser ver  pr otocol but they ar e most commonly used with HTTP and the wor d "Ser vlet" is of ten used in the meaning of "HTTP Ser vlet". Ser vlets mak e use of the Java standar d extension classes in the pack ages  javax. ser vlet (the basic Ser vlet f r amewor k ) and javax. ser vlet .htt p



Ty pical uses f or HTTP Ser vlets include: o

Pr ocessing and/or stor ing data su bmitted by an HTML f or m.

o

Pr oviding dynamic content, e.g. r etur ning the r esults of a data base quer y to the client.

o

Managing state inf or mation on to p of the stateless HTTP, e.g. f or an online sho p ping car t system which manages sho p ping car ts f or many concur r ent customer s and ma ps ever y r equest to the r ight customer .

6.1 Servlet Lif e Cycle

The lif e cycle of a ser vlet is contr olled by the container in which the ser vlet has been de ployed. When a r equest is ma p ped to a ser vlet, the container  per f or ms the f ollowing ste ps: 1. If an instance of the ser vlet does not exist, the we b container : a. Loads the ser vlet class  b. Cr eates an instance of the ser vlet class c. Initializes the ser vlet instance by calling the init method. Initialization is cover ed in Initializing a Ser vlet 2. Invok es the ser vice method, passing a r equest and r es ponse o b ject. 3. If the container needs to r emove the ser vlet, it f inalizes the ser vlet by calling the ser vlet’s destr oy method. 6.1.1 A servlet example

SJBIT, Dept . of ISE

Page 55

Java and J2EE (06IS753) im por t java.io.*; im por t javax.ser vlet.*; im por t javax.ser vlet.htt p. *;  pu blic class HelloClientSer vlet extends Htt pSer vlet {  pr otected void doGet(Htt pSer vletR equest r eq, Htt pSer vletR es ponse r es) thr ows Ser vletExce ption, IOExce ption { res.setContentTy pe("text/html"); Pr intWr iter out = r es.getWr iter (); out p . r intln(""+ "Hello Client !"); out.close(); }  pu blic Str ing getSer vletInf o() { retur n "HelloClientSer vlet 1.0 by Stef an Zeiger "; } } 6.1.2. Servlet API 



Two pack ages contain the classes and inter f aces that ar e r equir ed to build ser vlets. They ar e  javax.ser vlet and javax.ser vlet.htt p. The javax.ser vlet and javax.ser vlet.htt p pack ages pr ovide inter f aces and classes f or wr iting ser vlets. All ser vlets must im plement the Ser vlet inter f ace, which def ines lif e cycle methods.

6.1.3 The servlet pack ages : 

The java x. ser vl et  pack a g e contains a num ber of classes and inter f aces that descr i be and def ine the contr acts between a ser vlet class and the r untime envir onment pr ovided f or an instance of such a class by a conf or ming ser vlet container .



The S er vl et inter f ace is the centr al a bstr action of the ser vlet API.

SJBIT, Dept . of ISE

Page 56

Java and J2EE (06IS753) All ser vlets im plement this inter f ace either  dir ectly, or  mor e commonly,  by extending a class that im plements the inter f ace.



The two classes in the ser vlet API that im plement the S er vl et  inter f ace ar e Gener i I S   E r vl et  and Ht t   pS er vl et .



For  most  pur   poses, develo per s will extend  H t t   pS er vl et  to im plement their  ser vlets while im plementing we b a p plications em ploying the HTTP pr otocol.



The basic S er vl et inter f ace def ines a ser vice method f or handling client r equests. This method is called f or each r equest that the ser vlet container r outes to an instance of a ser vlet.



6.1.4 Handling HTTP requests and responses : 

Ser vlets can be used f or handling both the GET R equests and the POST R equests.

The Htt pSer vlet class is used f or  handling HTTP GET R equests as it has som s pecialized methods that can ef f iciently handle the HTTP r equests. These methods ar e; 

doGet() doPost() doPut() doDelete() doO ptions() doTr ace() doHead() An individual develo ping ser vlet f or handling HTTP R equests needs to over r ide one of these methods in or der to pr ocess the r equest and gener ate a r es ponse. The ser vlet is invok ed dynamically when an end-user su bmits a f or m. Example:

Select the color : Blue Or ange Her e’s the code f or ColSer vlet j . ava that over r ides the doGet() method to r etr ieve data f r om the HTTP R equest and it then gener ates a r es ponse as well. // im por t the java pack ages that ar e needed f or the ser vlet to wor k  im por t java.io .*; im por t javax.ser vlet. *; im por t javax.ser vlet.htt p. *; SJBIT, Dept . of ISE

Page 57

Java and J2EE (06IS753) // def ining a class  pu blic class ColSer vlet extends Htt pSer vlet {  pu blic void doGet(Htt pSer vletR equest r equest,Htt pSer vletR es ponse r es ponse) thr ows Ser vletExce ption, IOExce ption // r equest is an o b ject of ty pe Htt pSer vletR equest and it's used to o btain inf or mation // r es ponse is an o b ject of ty pe Htt pSer vletR es ponse and it's used to gener ate a r es ponse // thr ows is used to s pecif y the exce ptions than a method can thr ow { Str ing colname = r equest.getPar ameter ("col"); // getPar ameter () method is used to r etr ieve the selection made by the user  res ponse.setContentTy pe("text/html"); Pr intWr iter inf o = r es ponse.getWr iter (); inf o  p . r intln("The color is: "); inf o  p . r intln(col); inf o.close(); } } 6.2 Cook ies

Cook ies ar e small bits of textual inf or mation that a We b ser ver sends to a br owser and that the  br owser r etur ns unchanged when visiting the same We b site or domain later . By having the ser ver r ead inf or mation it sent the client pr eviously, the site can pr ovide visitor s with a num ber of conveniences lik e: 

Identif ying a user dur ing an e-commer ce session..



Avoiding user name and passwor d.



Customizing a site.



Focusing adver tising.

To send cook ies to the client, a ser vlet would cr eate one or mor e cook ies with the a p pr o pr iate names and values via new Cook ie (name, value) 6.2.1 Placing Cook ies in the R esponse Headers

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) 

The cook ie is added to the Set-Cook ie r es ponse header  by means of the addCook ie method of Htt pSer vletR es ponse. For exam ple: Cook ie user Cook ie = new Cook ie("user ", "uid 1234"); r es ponse.addCook ie(user Cook ie);







To send cook ies to the client, you cr eated a Cook ie then used addCook ie to send a SetCook ie HTTP r es ponse header . To r ead the cook ies that come back f r om the client, call getCook ies on the Htt pSer vletR equest. This r etur ns an ar r ay of Cook ie o b jects cor r es ponding to the values that came in on the Cook ie HTTP r equest header  Once this ar r ay is o btained, loo p down it, calling get Name on each Cook ie until f ind one matching the name you have in mind. You then call getValue on the matching Cook ie, doing some pr ocessing s pecif ic to the r esultant value.  pu blic static Str ing getCook ieValue(Cook ie[] cook ies, Str ing cook ie Name, Str ing def aultValue) { for (int i=0; i






Session Track ing

Why id it needed : In many inter net a p plications it is im por tant to k ee p tr ack of the session when the user moves f r om one page to another or when ther e ar e dif f er ent user s logging on to the same we bsite at the same time Ther e ar e thr ee ty pical solutions to this pr o blem.

Cook ies. 

HTTP cook ies can be used to stor e inf or mation a bout a sho p ping session, and



each su bsequent connection can look u p the cur r ent session and then extr act



inf or mation a bout that session f r om some location on the ser ver machine.



This is an excellent alter native, and is the most widely used a p pr oach.

SJBIT, Dept . of ISE

Page 59

Java and J2EE (06IS753) UR L R ewriting. 













You can a p pend some extr a data on the end of each UR L that identif ies the session, and the ser ver can associate that session identif ier with data it has stor ed a bout that session. This is also an excellent solution, and even has the advantage that it wor k s with br owser s that don't su p por t cook ies or wher e the user has disa bled cook ies. However , it has most of the same pr o blems as cook ies, namely that the ser ver -side pr ogr am has a lot of str aightf or war d but tedious pr ocessing to do. In addition, you have to be ver y car ef ul that ever y UR L r etur ned to the user (even via indir ect means lik e Hidden f or m f ields. HTML f or ms have an entr y that look s lik e the f ollowing: . This means that, when the f or m is su bmitted, the s pecif ied name and value ar e included in the GET or POST data. This can be used to stor e inf or mation a bout the session. 

However , it has the ma jor disadvantage that it only wor k s if ever y page is dynamically gener ated, since the whole point is that each session has a unique identif ier .

• Ser vlets solution : 



The Htt pSession API. is a high-level inter f ace built on to p of cook ies or UR Lr ewr iting. In f act, on many ser ver s, they use cook ies if the br owser su p por ts them, but automatically r ever t to UR L-r ewr iting when cook ies ar e unsu p por ted or ex plicitly disa bled. The ser vlet author doesn't need to bother with many of the details, doesn't have to ex plicitly mani pulate cook ies or inf or mation a p pended to the UR L, and is automatically given a convenient place to stor e data that is associated with each session.

exam ple, Htt pSession session = r equest.getSession(tr ue); Sho p pingCar t pr eviousItems = (Sho p pingCar t)session.getValue(" pr eviousItems"); if ( pr eviousItems != null) { doSomethingWith( pr eviousItems); } else {  pr eviousItems = new Sho p pingCar t(...); doSomethingElseWith( pr eviousItems); } SJBIT, Dept . of ISE

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Java and J2EE (06IS753) UNIT-7: JSP, R MI

Java Server Pages (JSP):

JSP, JSP Tags, Tomcat, R equest Str ing, User Sessions, Cook ies, Session O b jects. Java R emote Method Invocation:

Remote Method Invocation conce pt; Ser ver side, Client side.

SJBIT, Dept . of ISE

Page 61

Java and J2EE (06IS753) 



JavaSer ver Pages (JSP) is a Sun Micr osystems s pecif ication f or com bining Java with HTML to pr ovide dynamic content f or We b pages. When you cr eate dynamic content, JSPs ar e mor e convenient to wr ite than HTTP ser vlets  because they allow to em bed Java code dir ectly into HTML  pages, in contr ast with HTTP ser vlets, in which you em bed HTML inside Java code.



JSP is par t of the Java 2 Enter   pr ise Edition (J2EE).



JSP ena bles to se par ate the dynamic content of aWe b page f r om its pr esentation.



It cater s to two dif f er ent ty pes of  develo per s: HTML develo per s, who ar e r es ponsi ble f or  the gr a phical design of the page, and Java develo per s, who handle the develo pment of sof twar e to cr eate the dynamic content.

7.1 JSP Tags

The f ollowing ta ble descr i bes the basic tags that you can use in a JSP page. Each shor thand tag has an XML equivalent. JSP Tag Scr i ptlet

Syntax <% java _ code %> . . . or use the XML equivalent: < js p:scr i ptlet>  java _ code

Dir ective

<% @ dir -t y pe d ir -at t r  %> . . . or use the XML equivalent: < js p:dir ective.d ir   _ t   y pe d ir   _ at t r />

 Dir ect ive s contain messages to the a p plication ser ver . A dir ective can also contain name/value pair attr i butes in the f or m attr =”value”, which pr ovides additional instr uctions to the a p plication ser ver .

Declar ations

<%! declar ation %> . . . or use XML equivalent... < js p:declar ation> declar ation; <%= ex pr ession %> . . . or use XML < js p:useBean ... >

Declar es a var ia ble or  method that can be r ef er enced by other  declar ations, scr i ptlets, or  ex pr essions in the page

Ex pr ession Actions Tomcat

SJBIT, Dept . of ISE

Description

Em beds Java sour ce code Scr i ptlet in your HTML  page. The Java code is executed and its out put is inser ted in sequence with the r est of the HTML in the page.

Def ines a Java that is Pr ovide access to

Page 62

Java and J2EE (06IS753) 





A pache Tomcat is an im plementation of the Java Ser vlet and JavaSer ver Pages technologies. The Java Ser vlet and JavaSer ver Pages s pecif ications ar e develo ped under the Java Community Pr ocess. A pache Tomcat is develo ped in an o pen and par tici pator y envir onment and r eleased under  the A pache Sof twar e Simple example

<% @ page inf o="a hello wor ld exam ple" %> < body bgcolor ="#f f f f f f " back gr ound=" back gr ound.gif "> <% @ include f ile="duk e banner .html" %> &n bs p;

Hello, Wor ld !

Request string

<%@ page im por t="hello. NameHandler " %> < js p:useBean id="my bean" sco pe=" page" class="hello. NameHandler " /> < js p :setPr o per ty name="my bean" pr o per ty="*" /> < body bgcolor ="#f f f f f f " back gr ound=" back gr ound.gif "> <% @ include f ile="duk e banner .html" %> &n bs p; SJBIT, Dept . of ISE

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Java and J2EE (06IS753)

My name is Duk e. What's your s?

< br > <% if ( r equest.getPar ameter ("user name") != null ) { %> <% @ include f ile="r es ponse j . s p" %> <% } %> The data the user  enter s is stor ed in the r equest o b ject, which usually im plements  javax.ser vlet.Htt pSer vletR equest (or  if  your  im plementation uses a dif f er ent  pr otocol, another  inter f ace that is su bclassed f r om  javax.ser vlet.Ser vletR equest). You can access the r equest o b ject dir ectly within a scr i ptlet. Sessions and Cook ies in JSP 

In JSP cook ie ar e the o b ject of the class javax.servlet.http.Cook ie.



This class is used to cr eates a cook ie, a small amount of inf or mation sent by a ser vlet to a We b br owser , saved by the br owser , and later sent back to the ser ver .



A cook ie has a name, a single value, and o ptional attr i butes such as a comment,  path and domain qualif ier s, a maximum age, and a ver sion num ber .

The getCook ies() method of the r equest o b ject r etur ns an ar r ay of Cook ie o b jects. Cook ies can  be constr ucted using the f ollowing code: SJBIT, Dept . of ISE

Page 64

Java and J2EE (06IS753) <% @ page language=" java" im por t=" java.util. *"%> <% Str ing user name=r equest.getPar ameter ("user name"); if (user name==null) user name=""; Date now = new Date(); Str ing timestam p = now.toStr ing(); Cook ie cook ie = new Cook ie ("user name",user name); cook ie.setMaxAge(365 * 24 * 60 * 60); res ponse.addCook ie(cook ie); %> < body> < p> Next Page to view the cook ie value< p> A bove code sets the cook ie and then dis plays a link to view cook ie page 7.2 RMI 





RMI a p plications ar e of ten com pr ised of two se par ate pr ogr ams: a ser ver and a client. A ty pical ser ver  a p plication cr eates a num ber  of  r emote o b jects, mak es r ef er ences to those remote o b jects accessi ble, and waits f or clients to invok e methods on those r emote o b jects. A ty pical client a p plication gets a r emote r ef er ence to one or  mor e r emote o b jects in the ser ver and then invok es methods on them. R MI pr ovides the mecahnism by which the ser ver  and the client communicate and  pass inf or mation  back  and f or th. Such an a p plications is sometimes r ef er r ed to as a distr i buted o b ject a p plication.

The java.rmi.R emote Interf ace :

In R MI, a r emote inter f ace is an inter f ace that declar es a set of  methods that may  be invok ed f r om a r emote Java vir tual machine. A r emote inter f ace must satisf y the f ollowing requir ements: • A r emote inter f ace must at least extend, either  dir ectly or  indir ectly, the inter f ace  java.r mi.R emote. • Each method declar ation in a r emote inter f ace must satisf y the r equir ements Server side and Client side

The inter f ace Ser ver R ef r e pr esents the ser ver -side handle f or a r emote o b ject im plementation.  pack age java.r mi.ser ver ; SJBIT, Dept . of ISE

Page 65

Java and J2EE (06IS753)  pu blic inter f ace Ser ver R ef extends R emoteR ef { R emoteStu b ex por tO b ject( java.r mi.R emote o b j, O b ject data) thr ows  java.r mi.R emoteExce ption; Str ing getClientHost() thr ows Ser ver   NotActiveExce ption; } 

The method ex por tO b ject f inds or cr eates a client stu b o b ject f or the

su p plied R emote o b ject im plementation ob j. 



The par ameter d at a contains inf or mation necessar y to ex por t the o b ject (such as por t num ber ). The method getClientHost r etur ns the host name of the cur r ent client. When called f r om a thr ead actively handling a r emote method invocation, the host name of the client invok ing the call is r etur ned.



If a r emote method call is not cur r ently being ser vice, then Ser ver   NotActiveExce ption is called.

Ther e is no s pecial conf igur ation necessar y to ena ble the client to send R MI calls thr ough a f ir ewall. The client can, however , disa ble the  pack aging of  R MI calls as HTTP r equests  by setting the java.r mi.ser ver .disa bleHtt p pr o per ty to equal the boolean value tr ue.

SJBIT, Dept . of ISE

Page 66

Java and J2EE (06IS753) UNIT – 8: ENTER PR ISE JAVA BEANS

Enter   pr ise java Beans De ployment Descr i ptor s Session Java Bean Entity Java Bean Message-Dr iven Bean The JAR File.

SJBIT, Dept . of ISE

Page 67

Java and J2EE (06IS753) ™

Def inition : Enter   pr ise JavaBeans (EJB) is a managed, ser ver -side com ponent ar chitectur e f or  modular constr uction of enter   pr ise a p plications. Enterprise JavaBeans (EJB) is a managed, ser ver -side com ponent ar chitectur e f or  modular  constr uction of enter   pr ise a p plications. The EJB s pecif ication is one of  sever al Java APIs in the Java EE s pecif ication. EJB is a ser ver -side model that enca psulates the business logic of  an a p plication. The EJB s pecif ication was or iginally develo ped in 1997  by IBM and later  ado pted [1]  by Sun Micr osystems (EJB 1.0 and 1.1) in 1999 and enhanced under  the Java Community Pr ocess as JSR 19 (EJB 2.0), JSR 153(EJB 2.1), JSR 220 (EJB 3.0) and JSR 318 (EJB 3.1).

The EJB s pecif ication intends to  pr ovide a standar d way to im plement the  back -end  b ' usiness' code ty pically f ound in enter   pr ise a p plications (as o p posed to 'f r ont-end' inter f ace code). Such code addr esses the same ty pes of  pr o blems, and solutions to these pr o blems ar e of ten r e peatedly re-im plemented  by  pr ogr ammer s. Enter   pr ise JavaBeans ar e intended to handle such common concer ns as per sistence, tr ansactional integr ity, and secur ity in a standar d way, leaving  pr ogr ammer s f r ee to concentr ate on the par ticular  pr o blem at hand. In a ty pical J2EE a p plication, Enter   pr ise JavaBeans (EJBs) contain the a p plication's  business logic and live  business data. Although it is  possi ble to use standar d Java o b jects to contain your  business logic and business data, using EJBs addr esses many of  the issues you would f ind  by using sim ple Java o b jects, such as scala bility, lif ecycle management, and state management. Ther e ar e thr ee dif f er ent ty pes of EJB that ar e suited to dif f er ent pur   poses: 

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Session EJB —A Session EJB is usef ul f or ma p ping business pr ocess f low (or equivalent a p plication conce pts). Ther e ar e two su b-ty pes of  Session EJB — stateless and statef ul re pr esent " pur e" f unctionality that is cr eated as it is needed. Entity EJB —An Entity EJB ma ps a com bination of  data (or  equivalent a p plication conce pt) and associated f unctionality. Entity EJBs ar e usually  based on an under lying data stor e and will be cr eated based on that data within it. Message-driven EJB —A Message-dr iven EJB is ver y similar  in conce pt to a Session EJB, but is only activated when an asynchr onous message ar r ives.

1. Deployment Descriptors

Def inition : A d e pl o yment  d e scr i pt or  is a f ile that def ines the f ollowing k inds of  inf or mation: EJB structural inf ormation, such as the EJB name, class, home and r emote inter f aces,  bean ty pe (session or  entity), envir onment entr ies, r esour ce f actor y r ef er ences, EJB r ef er ences, secur ity r ole r ef er ences, as well as additional inf or mation  based on the  bean ty pe. Application assembly inf ormation, such as EJB r ef er ences, secur ity r oles, secur ity r ole r ef er ences, method  per missions, and container tr ansaction attr i butes. S pecif ying assem bly descr i ptor inf or mation is an o ptional task that an A p plication Assem bler  per f or ms. 1.1 Session Bean SJBIT, Dept . of ISE

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Java and J2EE (06IS753) Session bean is a ty pe of enter   pr ise bean; a ty pe of EJB ser ver -side com ponent.

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Session bean com ponents im plement the javax.e j b.SessionBean inter f ace and can be stateless or statef ul. Stateless session beans ar e com ponents that per f or m tr ansient ser vices; statef ul session  beans ar e com ponents that ar e dedicated to one client and act as a ser ver -side extension of  that client.

Session beans can act as agents modeling wor k f low or  pr ovide access to s pecial tr ansient  business ser vices. As an agent, a statef ul session bean might r e pr esent a customer 's session at an online sho p ping site. 

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As a tr ansitive ser vice, a stateless session bean might pr ovide access to validate and  pr ocess cr edit car d or der s. Session beans do not nor mally r e pr esent per sistent business conce pts lik e Em ployee or Or der . This is the domain of a dif f er ent com ponent ty pe called an entity bean.

Example : pack age e j b.demo;

im por t javax.e j b.*; im por t java.r mi.R emote; im por t java.r mi.R emoteExce ption; im por t java.util. *; /* * * This inter f ace is extr emely sim ple it declar es only * one cr eate method. */  pu blic inter f ace DemoHome extends EJBHome {  pu blic Demo cr eate() thr ows Cr eateExce ption, R emoteExce ption; } Entity Java Bean 

An ent it   y bean re pr esents a business o b ject in a per sistent stor age mechanism.

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Some exam ples of  business o b jects ar e customer s, or der s, and pr oducts.

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In the J2EE SDK , the per sistent stor age mechanism is a r elational data base.

Ty pically, each entity bean has an under lying ta ble in a r elational data base, and each instance of the bean cor r es ponds to a r ow in that ta ble. 

Message-Driven Bean SJBIT, Dept . of ISE

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Java and J2EE (06IS753) 

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A me s sa g e-d r iven bean is an enter   pr ise bean that allows J2EE a p plications to pr ocess messages asynchr onously. It acts as a JMS message listener , which is similar to an event listener exce pt that it receives messages instead of events. The messages may be sent by any J2EE com ponent--an a p plication client, another  enter   pr ise bean, or a We b com ponent--or  by a JMS a p plication or system that does not use J2EE technology.

Message-dr iven beans cur r ently pr ocess only JMS messages, but in the f utur e they may be used to  pr ocess other k inds of messages The JAR f ile

The Java Ar chive (JAR ) f ile f or mat ena bles you to bundle multi ple f iles into a single ar chive f ile. Ty pically a JAR f ile contains the class f iles and auxiliar y r esour ces associated with a p plets and a p plications. The JAR f ile f or mat pr ovides many benef its: 

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S ecur it   y: You can digitally sign the contents of a JAR f ile. User s who r ecognize your  signatur e can then o ptionally gr ant your sof twar e secur ity pr ivileges it wouldn't other wise have.  Decr ea sed d ownl oad t ime: If your a p plet is bundled in a JAR f ile, the a p plet's class f iles and associated r esour ces can be downloaded to a br owser in a single HTTP tr ansaction without the need f or o pening a new connection for each f ile. C om pr e s sion: The JAR f or mat allows you to com pr ess your f iles f or ef f icient stor age.  P ack a g in g  f or e xt en sion s: The extensions f r amewor k  pr ovides a means by which you can add f unctionality to the Java cor e platf or m, and the JAR f ile f or mat def ines the pack aging f or extensions. By using the JAR f ile f or mat, you can tur n your sof twar e into extensions as well.  P ack a g e S eal in g : Pack ages stor ed in JAR f iles can be o ptionally sealed so that the pack age can enf or ce ver sion consistency. Sealing a pack age within a JAR f ile means that all classes def ined in that pack age must be f ound in the same JAR f ile.  P ack a g e V er   sionin g : A JAR f ile can hold data a bout the f iles it contains, such as vendor  and ver sion inf or mation.  P or t abil it   y: The mechanism f or handling JAR f iles is a standar d par t of the Java platf or m's cor e API.

Execution SJBIT, Dept . of ISE

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Java and J2EE (06IS753) EJBs ar e de ployed in an EJB container , ty pically but not necessar ily, within an a p plication ser ver . The s pecif ication descr i bes how an EJB inter acts with its container  and how client code inter acts with the container /EJB com bination. The EJB classes used  by a p plications ar e included in the javax.e jb pack age. (The javax.e j b.s pi pack age is a ser vice  pr ovider  inter f aceused only  by EJB container im plementations.) Clients of  EJB  beans do not instantiate those  beans dir ectly via Java's new o per ator ,  but instead have to o btain a r ef er ence via the EJB container . This r ef er ence is then not a r ef er ence to the im plementation  bean itself ,  but to a pr oxy, which either  dynamically im plements the local or  remote  business inter f ace that the client r equested or  dynamically im plements a sub-ty pe of  the actual  bean. The  pr oxy can then be dir ectly cast to the inter f ace or  bean. A client is said to have a 'view' on the EJB, and the local inter f ace, r emote inter f ace and  bean ty pe itself  r es pectively cor r es pond with the local view, r emote view and no-inter f ace view. This  pr oxy is needed in or der  to give the EJB container  the o p por tunity to tr ans par ently  pr ovide cr oss-cutting (AOP-lik e) ser vices to a  bean lik e tr ansactions, secur ity, inter ce ptions, in jections, remoting, etc. E.g. a client invok es a method on a  pr oxy, which will then f ir st star t a tr ansaction with the hel p of  the EJB container and then call the actual  bean method. When the actual  bean method r etur ns, the  pr oxy ends the tr ansaction (i.e.  by committing it or  doing a r oll back ) and tr ansf er s contr ol  back  to the client. Transactions

EJB container s must su p por t  both container  managed ACID tr ansactions and  bean managed tr ansactions. Container -managed tr ansactions (CMT) ar e  by def ault active f or calls to session beans. That is, no ex plicit conf igur ation is needed. This  behavior  may  be declar atively tuned  by the  bean via annotations and if  needed such conf igur ation can later  be over r idden in the de ployment descr i ptor . Tuning includes switching of f  tr ansactions f or  the whole  bean or  s pecif ic methods, or  r equesting alter native str ategies f or  tr ansaction  pr o pagation and star ting or   joining a tr ansaction. Such str ategies mainly deal with what should ha p pen if a tr ansaction is or isn't alr eady in pr ogr ess at the time the bean is called. The f ollowing var iations ar e su p por ted: Declarative Transactions Management Types Type

Explanation

MA NDATOR Y

If the client has not star ted a tr ansaction, an exce ption is thr own. Other wise the client's tr ansaction is used.

REQUIR ED

If the client has star ted a tr ansaction, it is used. Other wise a new tr ansaction is star ted. (this is the def ault when no ex plicit ty pe has been s pecif ied)

SJBIT, Dept . of ISE

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Java and J2EE (06IS753)

REQUIR ES _   NEW

If the client has star ted a tr ansaction, it is sus pended. A new tr ansaction is always star ted.

SUPPOR TS

If the client has star ted a tr ansaction, it is used. Other wise, no tr ansaction is used.

 NOT _ SUPPOR TED

If the client has star ted a tr ansaction, it is sus pended. No new tr ansaction is star ted.

 NEVER 

If the client has star ted a tr ansaction, an exce ption is thr own. No new tr ansaction is star ted.

Alter natively, the  bean can also declar e via an annotation that it wants to handle tr ansactions  pr ogr ammatically via the JTA API. This mode of  o per ation is called Bean Managed Tr ansactions (BMT), since the bean itself handles the tr ansaction instead of the container . Events

JMS (Java Message Ser vice) is used to send messages f r om  beans to clients, to let clients r eceive asynchr onous messages f r om these  beans. MDBs can  be used to r eceive messages f r om clients asynchr onously using either a JMS Queue or a To pic. Naming and directory services

As an alter native to in jection, clients of  an EJB can o btain a r ef er ence to the session  bean's  pr oxy o b ject (the EJB stu b) using J NDI. This alter native can  be used in cases wher e in jection is not availa ble, such as non-managed beans or standalone r emote Java SE clients, or when it's necessar y to pr ogr ammatically deter mine which bean to o btain. J NDI names f or EJB session beans ar e assigned by the EJB container via the f ollowing scheme: JNDI names Scope

Name pattern

Glo bal

 java:glo bal[/]//< bean-name>[!]

A p plication  java:a p p//< bean-name>[!] Module

 java:module/< bean-name>[!]

( ent r ie s in squar e br ack et   s d enot e o pt ional  par t   s ) A single  bean can  be o btained  by any name matching the a bove  patter ns, de pending on the 'location' of  the client. Clients in the same module as the r equir ed  bean can use the module sco pe

SJBIT, Dept . of ISE

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Java and J2EE (06IS753) and lar ger  sco pes, clients in the same a p plication as the r equir ed  bean can use the a p p sco pe and higher , etc.

SJBIT, Dept . of ISE

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